All EFL Clubs must name at least 1 player who has come through Academy (must have been registered with club for at least 1 year upto U19s) in there Match day Squad
What happens if you sell him in January. We dont have any regular squad members who qualify at the moment I dont think - though I guess the important question is do we have any coming through who are good enough to be in the squad but not too good so we have to sell them
There will be a lot of young players warming the bench with zero prospect of getting a game then. All this will effectively do is reduce the number of subs a manager has to pick from.